Competition - post a photo you've taken of nature >>

Dot and cross diagram need help

coconut64

Have I done this right? It seems a bit different from the other diagrams I found. Thanks

(edited 7 years ago)

Reply 1

username2337813

I don't think you've attached anything for anyone to look at...

Reply 2

coconut64

Original post by hxfsxh

I don't think you've attached anything for anyone to look at...

Just uploaded it, didn't expect a speedy reply. Thanks

Reply 3

alow

Original post by coconut64

Just uploaded it, didn't expect a speedy reply. Thanks

What exactly are we looking at? The hydroxides look okay, so does the (I'm guessing) calcium.

Reply 4

coconut64

Original post by alow

What exactly are we looking at? The hydroxides look okay, so does the (I'm guessing) calcium.

Sorry this is just rough work, this is a dot and cross diagram for Ca(OH)2. So I have done it right?

Reply 5

alow

Original post by coconut64

Sorry this is just rough work, this is a dot and cross diagram for Ca(OH)2. So I have done it right?

I'd say so. Why do you think it isn't okay?

Reply 6

coconut64

Original post by alow

I'd say so. Why do you think it isn't okay?

Hi, this picture seems to show that there is a dative covalent bond between O and H but in my diagram it is a covalent bond so H shares electrons with O. In the picture there are 2 crosses between o and H but in mine it is a dot and a cross.

The next part of the question ask how many moles of electrons are there in the Oh- ions in this compound. From my diagram, I can only see that there are 8 electrons in the Oh- ion, but the answer is 10 which I am really confused about.

Thanks

Reply 7

alow

Original post by coconut64

Hi, this picture seems to show that there is a dative covalent bond between O and H but in my diagram it is a covalent bond so H shares electrons with O. In the picture it is 2 dots between o and H but in mine it is a dot and a cross.

The next part of the question ask how many moles of electrons are there in the Oh- ions in this compound. From my diagram, I can only see that there are 8 electrons in the Oh- ion, but the answer is 10 which I am really confused about.

Thanks

Yeah the O-H bond definitely should have 1 electron from the hydrogen. The Ca only gives two electrons in total, one to each hydroxide.

What's the exact wording of the question?

Reply 8

coconut64

Original post by alow

Yeah the O-H bond definitely should have 1 electron from the hydrogen. The Ca only gives two electrons in total, one to each hydroxide.

What's the exact wording of the question?

Great. So I believe I have drawn it correctly?

Reply 9

alow

Original post by coconut64

Great. So I believe I have drawn it correctly?

Yeah.

Reply 10

coconut64

Original post by alow

Yeah the O-H bond definitely should have 1 electron from the hydrogen. The Ca only gives two electrons in total, one to each hydroxide.

What's the exact wording of the question?

chem question.pdf I am referring to 2b in this picture where it asks about the Ca(Oh)2 compound. I know that there are 3 moles of ions in this compound but I don't get next part of the question 2biii)

Thanks !

Reply 11

alow

Original post by coconut64

Think about the electron configuration of oxygen. There are 8 valence electrons in a hydroxide ion, but those aren't the only electrons.

Reply 12

coconut64

Original post by alow

Think about the electron configuration of oxygen. There are 8 valence electrons in a hydroxide ion, but those aren't the only electrons.

Right. So Oh- ion has 8 electrons but since oxygen has 2 more electrons in its inner shell, this is why it adds up to 10?

Reply 13

alow

Original post by coconut64

Right. So Oh- ion has 8 electrons but since oxygen has 2 more electrons in its inner shell, this is why it adds up to 10?

Exactly.

Reply 14

coconut64

Original post by alow

Exactly.

I don't really get what it actually means by one mole of electrons. Initially, I just did 1*6.02*10^23, do you only do it when it asks for number of atoms in the ions?

Reply 15

alow

Original post by coconut64

I don't really get what it actually means by one mole of electrons. Initially, I just did 1*6.02*10^23, do you only do it when it asks for number of atoms in the ions?

A mole is just an amount. You could have a mole of elephants or a mole of bananas.

So when you're asked how many moles of something there are in a mole of a compound it's just a case of counting them.